Nutrients not converted to agricultural products are at risk of being lost to the environment and can contribute to environmental degradation. The adoption of nutrient management planning (NMP) can lead to win-win outcomes in terms of both improving productivity and reducing the environmental impact of farming, yet adoption remains below expectations globally. Few studies specifically focus on the adoption of NMP and the majority overlook psychological factors in their analysis. This study examines the factors which influence Irish farmers’ intention to adopt NMP as defined by intention to apply fertiliser on the basis of soil test results. An expanded version of the theory of planned behaviour is used as a framework for analysis. The influence of policy is also accounted for by this study which requires certain farmers in Ireland to adopt soil testing on a mandatory basis. The results for the national sample (n=1009) show that attitudes, subjective norms (social pressure), perceived behavioural control (ease/difficulty) and perceived resources are significant and positively associated with farmers’ intentions. In terms of the voluntary sample (n=587), only attitude, perceived behavioural control and perceived resources are significantly and positively associated with farmers’ intentions. Whereas, for the mandatory sample (n=422), subjective norms, perceived behavioural control and perceived resources are significantly and correlated in a positive direction with intentions. A number of farm and farmer characteristics were also significantly associated with intentions. We argue that psychological issues must be addressed by initiatives designed to encourage further uptake of NMP. Furthermore, initiatives must account for the heterogeneity in the factors which influence farmers to adopt, which may be influenced by motivations for adopting soil testing, such as voluntary or mandatory purposes.